CN111207000B

CN111207000B - Method for diagnosing an internal combustion engine for leaks in sections of a fresh gas line

Info

Publication number: CN111207000B
Application number: CN201911125490.7A
Authority: CN
Inventors: M.豪普沃格尔; F.贝尔斯基
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2018-11-21
Filing date: 2019-11-18
Publication date: 2022-08-16
Anticipated expiration: 2039-11-18
Also published as: CN111207000A; US11428597B2; EP3656993A1; DE102018219970A1; US20200158590A1

Abstract

The invention relates to a method for diagnosing an internal combustion engine having a combustion engine (1) and a fresh gas line (5), fresh gas being feedable into the combustion engine (1) via the fresh gas line (5), wherein a fresh gas compressor (8) and a control valve (15) upstream of the fresh gas compressor (8) are integrated in the fresh gas line (5), characterized in that the control valve (15) is closed to such an extent that a negative pressure compared to the ambient pressure is generated by the operating combustion engine (1) in a section of the fresh gas line (5) between the control valve (15) and the combustion engine (1), wherein the actual value corresponding to the negative pressure is compared with a target value, and it is concluded from the difference between the actual value and the target value whether a leak is present in the section of the fresh gas line (5).

Description

Method for diagnosing an internal combustion engine for leaks in sections of a fresh gas line

Technical Field

The invention relates to a method for diagnosing a supercharged internal combustion engine for leaks in sections of a fresh gas line.

Background

Internal combustion engines used to drive motor vehicles are typically supercharged in order to increase the specific power output and reduce the specific fuel consumption. Supercharging of internal combustion engines by means of one or more exhaust-gas turbochargers is widely used. Such exhaust gas turbochargers comprise an exhaust gas turbine with a turbine wheel which is driven in rotation by an inflow of exhaust gas discharged from a combustion engine of the internal combustion engine. The turbine wheel drives a compressor wheel of a fresh gas compressor via a shaft, the fresh gas compressor is integrated in a fresh gas line of the combustion engine and the fresh gas is compressed by the fresh gas compressor. Alternatively, such a fresh gas compressor can also be driven by a different drive, for example the combustion engine itself or an electric motor. Furthermore, the quantity of fresh gas introduced into the combustion chamber of the combustion engine can be increased by the compression, and the quantity of fuel that can be converted in the combustion chamber per operating cycle can therefore be increased.

The drive speed of the compressor wheel is dependent not only on the drive power provided for this purpose but also on the drive resistance. The driving resistance is in turn directly related to the charging pressure in the charge air section, i.e. the pressure of the fresh gas in that section of the fresh gas line which is located between the fresh gas compressor and the combustion engine. In principle, therefore, the limitation of the operating speed of the fresh gas compressor (and therefore of the exhaust gas turbine in the case of an exhaust gas turbocharger) to the maximum permissible speed results in the internal combustion engine additionally having a specific operating state of the specific drive speed resulting in a specific charging pressure. Such a relationship can be adequately derived if the charge air section is sufficiently sealed. If such a seal is not provided sufficiently, a pressure loss and thus a reduction in the drive resistance can result, which in turn can lead to an exceeding of the maximum permissible rotational speed of the fresh gas compressor.

In principle, a leak in the charge air section of the fresh gas line of the internal combustion engine can be detected by pressure measurement and comparison of the measured actual value with a defined target value. But due to the constraints of the principle, this is only possible in operating conditions where boost pressure is actually generated by the compressor. However, many internal combustion engines for driving motor vehicles are often not operated in operating states in which a (high) charging pressure is present. Furthermore, this method can only detect leaks in the charge air section of the fresh gas line.

DE 102005024984 a1 describes an internal combustion engine having a combustion engine, a fresh gas line, a fresh gas compressor integrated in the fresh gas line, an exhaust gas aftertreatment device integrated in the exhaust gas line, a high-pressure exhaust gas recirculation system, a low-pressure exhaust gas recirculation system and a respective throttle valve, which is integrated in the fresh gas line upstream of a connecting opening of the respective exhaust gas recirculation system. In the warm-engine operation and/or low-load operation of the internal combustion engine, the amount of fresh gas supplied to the combustion engine via the fresh gas line is throttled by the throttle valve in order to increase the exhaust gas temperature in the exhaust gas line and thus to improve the efficiency of the exhaust gas aftertreatment device.

DE 102005060350 a1 discloses a method for controlling the combustion process of an internal combustion engine with an exhaust gas recirculation system, the combustion engine of which can be operated with different air-fuel ratios. In this case, the fresh air quantity and the recirculated exhaust gas flow are metered in a targeted manner, so that an accurate determination of the exhaust gas recirculation rate with low tolerance errors can be achieved.

DE 102015202180 a1 also describes a method by which the amount of air fed into a combustion engine with an exhaust gas recirculation system is regulated.

Disclosure of Invention

The object of the present invention is to provide an advantageous possibility for diagnosing an internal combustion engine with regard to the presence of a leak in the fresh gas line.

The object is achieved according to the invention by a method for diagnosing an internal combustion engine having a combustion engine and a fresh gas line, through which fresh gas can be supplied to the combustion engine, wherein a fresh gas compressor and a control valve upstream of the fresh gas compressor are integrated in the fresh gas line, wherein the control valve is closed to such an extent that a negative pressure compared to the ambient pressure is generated in a section of the fresh gas line between the control valve and the combustion engine by the operating combustion engine, wherein an actual value corresponding to the negative pressure is compared with a setpoint value, and it is concluded from the difference between the actual value and the setpoint value whether a leak is present in the section of the fresh gas line.

According to the invention, a method for diagnosing an internal combustion engine is specified, wherein the internal combustion engine comprises at least one combustion engine (in particular a (self-igniting and quality-controlled) diesel engine or a (ex-ignition and quantity-controlled) gasoline engine or a combination thereof, i.e. a combustion engine with homogeneous compression ignition) and a fresh gas line, via which fresh gas can be supplied to the combustion engine. At least one fresh gas compressor and a control valve (relative to the flow of fresh gas in the direction of the combustion engine) upstream of the fresh gas compressor are also integrated in the fresh gas line. In the operating state of the internal combustion engine, the control valve is closed to a certain extent (partially or completely or to the greatest possible extent) so that a negative or low pressure is generated in the section of the fresh gas line between the control valve and the combustion engine by the operating combustion engine in comparison with the ambient pressure, wherein a (measured) actual value corresponding to the negative pressure is compared with a setpoint value, and from the difference between the actual value and the setpoint value, which is present in some cases, it is concluded whether a leak is present in this section of the fresh gas line. In this case, it can be provided that, when the position of the control valve is set in a defined manner, the measured pressure actual value is compared with a pressure setpoint value, wherein a difference between this (in some cases larger absolute) pressure actual value and (in some cases smaller absolute) pressure setpoint value which exceeds a limit value is determined as a leak. In this case, it can also be provided that the size of the leak is inferred from the magnitude of the difference. Alternatively, it is advantageously possible to compare the actual position of the control valve, in which the control valve is in some cases closed to a greater extent, with the setpoint position of the control valve, in which the control valve is in some cases closed to a lesser extent, when the vacuum is set at a defined pressure value, wherein a difference between the actual position and the setpoint position which exceeds a limit value is determined as a leak. It may also be provided here that a specific size of the leakage or a specific degree of leakage is inferred from the difference.

According to the invention, the term "control valve" is understood to mean any actively actuatable component by means of which the influence on the gas flow flowing into the fresh gas line and guided through the control valve can be achieved. The control valve can preferably be designed in the form of a rotary valve, but can also have other designs.

It can be provided that the method or the generation of the negative pressure according to the invention is carried out when the internal combustion engine is in an operating state in which no pressure increase is produced by means of the fresh gas compressor, since the defined negative pressure can then be generated relatively quickly by closing the control valve and can also become relatively large. Thereby, on the one hand the speed with which the detection results can be obtained can be favorably influenced, and on the other hand the accuracy of the detection results can be favorably influenced. The operating state of the internal combustion engine without a boost pressure being generated by means of the fresh gas compressor is distinguished by the fact that no higher fresh gas pressure is present on the outlet side of the fresh gas compressor than on the inlet side. Such operating states are, in particular, a coasting operation with a gear of the internal combustion engine (when the combustion engine does not output drive energy but consumes drive energy) and an idling operation (when the internal combustion engine supplies drive energy at a minimum rotational speed but the drive energy is not branched). When the combustion engine is operated at a lower intake manifold pressure, it can also be operated in the corresponding low load range.

Preferably, when a request for a diagnosis is made (which may be made in particular by a control device of the internal combustion engine), the method according to the invention is not carried out or a negative pressure is generated until an operating state occurs spontaneously (i.e. not due to an active setting only for the purpose of diagnosis) in which the internal combustion engine does not generate a boost pressure. The method according to the invention is therefore not carried out until the internal combustion engine has been operated in the respective operating state as a result of the respective use by a user of a motor vehicle comprising the internal combustion engine, in particular by a driver of the motor vehicle. In this way, adverse effects on the operating behavior due to the active setting (in particular by means of the control device) of operating states which do not generate a boost pressure, which operating states do not correspond in any way to the operating states requested by the user of the internal combustion engine, can be avoided. However, in some cases, it is also possible to provide for an active setting of the operating state of the internal combustion engine in which no supercharging takes place.

The method according to the invention can also be used in an advantageous manner in internal combustion engines in which an exhaust gas recirculation line branching off from an exhaust gas line, via which exhaust gases of the combustion engine can be discharged, communicates with a fresh gas line. In this case, however, the exhaust gas recirculation valve integrated in the exhaust gas recirculation line should be kept at least partially, preferably completely or as far as possible closed during the generation of the negative pressure, in order not to make it difficult to generate a negative pressure due to the inflow of exhaust gas recirculated via the exhaust gas recirculation line or to avoid a distortion of the detection result due to recirculated exhaust gas.

In this case, the exhaust gas recirculation line can be provided on the one hand for a high-pressure exhaust gas recirculation system in which recirculated exhaust gas is introduced into the fresh gas line downstream of the fresh gas compressor (with respect to the flow of fresh gas in the fresh gas line in the direction of the combustion engine) and in some cases (i.e. in the case of the fresh gas compressor being designed as a component of a turbocharger) branches off from the exhaust gas line upstream of an exhaust gas turbine of the exhaust gas turbocharger which is integrated in the exhaust gas line (with respect to the flow of exhaust gas from the combustion engine in the exhaust gas line). On the other hand, the exhaust gas recirculation line can also be provided for a low-pressure exhaust gas recirculation system in which recirculated exhaust gas is introduced into the fresh gas line upstream of the fresh gas compressor and in some cases branches off downstream of an exhaust gas turbine integrated in the exhaust gas line. In principle, at least two exhaust gas recirculation lines can also be provided, at least one of which is used for the high-pressure exhaust gas recirculation system and at least one of which is used for the low-pressure exhaust gas recirculation system.

Preferably, the exhaust gas recirculation line or at least one of the two exhaust gas recirculation lines can open into a section of the fresh gas line between the control valve and the fresh gas compressor and can therefore be used in particular for low-pressure exhaust gas recirculation. In this case, it can also be provided that the exhaust gas recirculation line communicates with the fresh gas line immediately downstream of the control valve and in particular at the shortest possible distance from the control valve, whereby the control valve can also be used, or primarily during operation of the internal combustion engine, to generate a local underpressure in the region of the communication opening of the exhaust gas recirculation line in order to ensure a sufficiently large exhaust gas flow recirculated via the exhaust gas recirculation line.

The method according to the invention can also be used advantageously in internal combustion engines in which a throttle valve is integrated in the section of the fresh gas line between the fresh gas compressor and the combustion engine. However, in this case, provision should be made for the throttle valve to be kept at least partially open, preferably completely open or as large as possible, during the generation of the negative pressure, in order to be able to generate the negative pressure also in the section of the fresh gas line between the control valve and the throttle valve by means of the operating combustion engine.

In the case of a combustion engine designed as a gasoline engine, the throttle can be used in particular for controlling the amount of fresh gas supplied to the combustion chamber of the combustion engine (i.e. for quantity control of the gasoline engine). In the case of a diesel engine, the throttle valve has at least the main function of rapidly closing the charge air section after the end of the operation of the diesel engine, so that a subsequent flow of compressed fresh gas into the combustion chamber of the diesel engine can be avoided. This prevents unintentional coasting of the diesel engine due to self-ignition of the residual fuel in the combustion chamber in the presence of fresh gas flowing in. If an exhaust gas recirculation line for a high-pressure exhaust gas recirculation system is also present in the internal combustion engine according to the invention having a throttle valve, this throttle valve can also be used to influence the exhaust gas recirculation rate.

If a leak in the fresh gas line is detected within the scope of the implementation of the method according to the invention, a fault record can preferably be generated in a fault memory, for example in a fault memory of an engine controller of the internal combustion engine. The fault record can then be read back immediately or at a later point in time in order to initiate measures for eliminating the leakage and/or compensating for the effects of the leakage.

In particular, it may be provided that, in the event of a leak being detected, measures for limiting the drive rotational speed of the fresh gas compressor are initiated. These measures can include, for example, adjusting the device for the variable inflow of the fresh gas compressor and/or the device for the variable inflow (or Variable Turbine Geometry) (VTG) of the exhaust gas turbine and/or the wastegate valve in such a way that the compression power generated by these devices and/or the wastegate valve in the event of a detected leakage is smaller than in the case of a setting in which no leakage is detected.

A particular advantage of the method according to the invention is that the method according to the invention can carry out or provide good diagnostic results even if the leakage is so small that the effects it has on normal operation of the internal combustion engine can/have been automatically compensated for by one or more boost pressure regulators, in particular VTGs and/or wastegate valves.

The internal combustion engine used in the context of the method according to the invention may be part of a motor vehicle, in particular a motor vehicle based on wheels and not running on rails, preferably a passenger car or a truck. In this case, the internal combustion engine can be provided in particular for directly or indirectly providing drive power for the motor vehicle.

In particular, the indefinite articles "a" and "an" in this specification should be understood as such and not as articles of manufacture. Accordingly, the components specifically identified thereby should be understood such that they occur at least once and may occur more than once.

Drawings

The invention is explained in detail below on the basis of embodiments shown in the drawings. In the drawings;

fig. 1 schematically shows an internal combustion engine suitable for implementing the method according to the invention.

Detailed Description

The internal combustion engine shown in fig. 1 includes a combustion engine 1, and the combustion engine 1 is configured with a plurality of cylinders 2. The cylinder 2 delimits, together with a piston 3 guided in the cylinder 2 to and fro up and down and a cylinder head (not shown), a combustion chamber in which fresh gas is combusted together with fuel. Here, fuel is directly injected into the combustion chamber by an injector (not shown) under the control of a control device 4 (engine controller). The combustion of the fuel-fresh gas mixture causes an up-and-down reciprocating movement of the piston 3, which in turn is transmitted in a known manner via a connecting rod, not shown, to a crankshaft, also not shown, whereby the crankshaft is driven in rotation.

Fresh gas is fed into the combustion engine 1 via a fresh gas line 5. For this purpose, air is taken from the environment through the intake 6, is subsequently cleaned in an air filter 7 and is then fed into a fresh gas compressor 8, the fresh gas compressor 8 being part of an exhaust gas turbocharger. Before this, the air can be mixed with the exhaust gas which is conducted through the exhaust gas recirculation line 9 in order to achieve low-pressure exhaust gas recirculation, whereby fresh gas of the mixture of air and recirculated exhaust gas is fed into the fresh gas compressor 8. The exhaust gas recirculation line 9 branches off from an exhaust gas line 10 and branches off in particular downstream of an exhaust gas turbine 11 integrated in the exhaust gas line 10, which exhaust gas turbine 11 is also part of an exhaust gas turbocharger, and the exhaust gas recirculation line 9 opens into the fresh gas line 5 upstream of the fresh gas compressor 8. Integrated in the exhaust gas recirculation line 9 is also an exhaust gas cooler 12 and an exhaust gas recirculation valve 13 which can be actuated by the control device 4. The recirculated exhaust gas can be cooled by means of an exhaust gas cooler 12 in order to keep the thermal load of the fresh gas compressor 8 low. The quantity of exhaust gas guided through the exhaust gas recirculation line 19 can be influenced or controlled by means of the exhaust gas recirculation valve 13.

In order to be able to set a sufficient pressure drop in the exhaust gas recirculation line 9 at any time during operation of the internal combustion engine, a control valve 15 is integrated in the section of the fresh gas line 5 between the air filter 7 and the connection 14 of the exhaust gas recirculation line 9, which control valve 15 is also actuated by the control device 4. By virtue of the gradual closing of the control valve 15 (as a result of which the control valve 15 gradually reduces the free flow cross section of the fresh gas line 5 at the control valve 15), a negative pressure can be generated in the region downstream of the flow valve 15 and thus in the region of the communication opening 14 of the exhaust gas recirculation line 9, which negative pressure also ensures a sufficient pressure drop over the exhaust gas recirculation line 9, in particular if no or only a small boost pressure in the charge air section (i.e. the section of the fresh gas line 5 between the fresh gas compressor 8 and the combustion engine 1) is generated by the fresh gas compressor 8, which boost pressure has a corresponding suction effect on the upstream side of the fresh gas compressor 8.

Fresh gas is compressed by the fresh gas compressor 8, subsequently cooled in the charge air cooler 16 and then fed into the combustion chamber under the control of the inlet valve 17. The fresh gas compressor 8 is driven by means of an exhaust gas turbine 11. Exhaust gases which are produced in the combustion chamber of the combustion engine 1 during combustion of the fuel-fresh gas mixture are discharged from the combustion engine 1 and via the exhaust gas line 10 under the control of the exhaust valve 18. The exhaust gas flows through the exhaust gas turbine 11. This causes a rotary drive of a turbine wheel (not shown) of the exhaust gas turbine 11, which is connected in a rotationally fixed manner via a shaft 19 to a compressor wheel (not shown) of the fresh gas compressor 8.

In order to achieve the best possible use of the enthalpy of the exhaust gas during operation of the combustion engine 1 at varying loads and speeds in order to generate compression power by means of an exhaust gas turbocharger, the exhaust gas turbine 11 may comprise a device for variable turbine inflow (VTG)20 which can be actuated by means of the control device 4. The device 20 for variable turbine inflow can comprise in a known manner a plurality of guide vanes which are arranged in the inlet channel of the exhaust gas turbine 11 and are designed to be individually rotatable, wherein the guide vanes can be moved by means of an adjusting device. Depending on the rotational position of the guide blades, these reduce the free flow cross section in the inlet channel of the exhaust gas turbine 11 to a greater or lesser extent and also influence the section of the turbine wheel which is predominantly impinged upon by the inflow and the orientation of the inflow. Alternatively, however, the exhaust gas turbine can also be designed without VTG and with or without a wastegate.

Downstream of the fresh gas compressor 8 and the charge air cooler 16 (also referred to as intercooler), a throttle valve 21, which can likewise be actuated by the control device 4, is integrated in the charge air section of the fresh gas line 5.

In order to check the section of the fresh gas line 5, in particular the section of the fresh gas line 5, which is located between the control valve 15 and the intake valve 17 of the combustion engine 1, with respect to the presence of a leak, it is provided according to the invention that, after such a diagnosis has been requested by the control device 4 (which may be provided, for example, once after each start of operation of the internal combustion engine), the control valve 15 is closed to a certain extent in an operating state of the internal combustion engine without a boost pressure generated by the fresh gas compressor 8, in particular during an idle operation or a coasting operation of the combustion engine 1, so that a negative pressure is generated in the section by the combustion engine 1 which is still operating, compared to the ambient pressure. The generation of this negative pressure is based on the combustion engine's action of sucking in fresh gas from the fresh gas line 5 and discharging it into the exhaust gas line 10, which action is caused by the periodic movement of the piston 3 and the periodic opening and closing of the inlet valve 17 and the exhaust valve 18, which negative pressure is also generated when the combustion engine 1 is operating in a coasting mode with gear in which no fresh gas-fuel mixture is combusted in the combustion chamber.

Such diagnostics may also be initiated passively, i.e. the diagnostics are not actively requested due to the presence of a certain parameter of the control unit. In this case, the respective operating state of the internal combustion engine can be set in particular randomly.

During the generation of the negative pressure, the egr valve 13 is completely closed to avoid recirculation of exhaust gases via the egr line 9, which would otherwise counteract the desired negative pressure in the fresh gas line 5. If the combustion engine 1 has a function for partial operation in which the combustion engine can in principle be operated with only a fraction of the total available combustion chambers (so-called cylinder deactivation), it should also be provided that this function is deactivated in order to achieve the greatest possible suction effect of the combustion engine 1.

Depending on the specifically set closed position of the control valve 15 and the operating speed of the combustion engine 1, a defined value or value range of the (negative) pressure in the section of the fresh gas line 5 should have been set after a defined time interval, which is stored as a setpoint value in the control device 4. If this setpoint value is reached at least approximately, which is measured by means of at least one pressure sensor 22 integrated in the section of the fresh gas line 5 (detection of the actual value), it is assumed that no leakage is present in the section of the fresh gas line 5. Therefore, the diagnosis is ended after the diagnosis result is stored in the control device 4 in some cases.

In contrast, if the target value is not reached or the detected actual value differs considerably from the target value and the difference is greater than a specified tolerance, it is assumed that a leak in the fresh gas line 5 is present in the section and a corresponding fault record is stored in the control device 4. This fault record can then be read during maintenance of the internal combustion engine or of a motor vehicle having the internal combustion engine and used as an incentive for repairing the fresh gas line 5. In addition, provision may be made for the control device 4 to switch to an emergency operating program for the subsequent diagnostic operation of the internal combustion engine, in which emergency operating program measures are taken to avoid exceeding the maximum permissible rotational speeds of the fresh gas compressor 8 and the exhaust gas turbocharger. In order to avoid exceeding the maximum permissible rotational speed of the exhaust gas turbocharger, provision may additionally be made for the control of the VTG 16 (or wastegate valve) to be changed in order to at least temporarily reduce the use of the exhaust gas enthalpy available in the exhaust gas turbine.

List of reference numerals

1 combustion engine

2 cylinder

3 piston

4 control device

5 fresh gas line

6 air suction inlet

7 air filter

8 fresh gas compressor

9 exhaust gas recirculation line

10 exhaust gas line

11 exhaust gas turbine

12 exhaust gas cooler

13 exhaust gas recirculation valve

14 communication port of exhaust gas recirculation line

15 control valve

16 charge air cooler

17 air intake valve

18 exhaust valve

19 shaft

Device for variable turbine inflow (VTG)

21 throttle valve

22 pressure sensor

Claims

1. A method for diagnosing an internal combustion engine having a combustion engine (1) and a fresh gas line (5), fresh gas being feedable into the combustion engine (1) via the fresh gas line (5), wherein a fresh gas compressor (8) and a control valve (15) upstream of the fresh gas compressor (8) are integrated in the fresh gas line (5), characterized in that the control valve (15) is closed to such an extent that a negative pressure compared to the ambient pressure is generated by the operating combustion engine (1) in a section of the fresh gas line (5) between the control valve (15) and the combustion engine (1), wherein the actual value corresponding to the negative pressure is compared with a target value, and it is concluded from the difference between the actual value and the target value whether a leak is present in the section of the fresh gas line (5).

2. Method according to claim 1, characterized in that the pressure actual value is compared with a pressure setpoint value when the position of the control valve (15) is determined.

3. Method according to claim 1, characterized in that the actual position of the control valve (15) is compared with the nominal position of the control valve (15) when the underpressure is set at a defined pressure value.

4. A method according to any one of claims 1-3, characterised in that the method is carried out in an operating state in which the internal combustion engine is not supercharged by means of the fresh gas compressor (8).

5. Method according to claim 4, characterized in that the method is carried out in an idle operating state of the internal combustion engine.

6. Method according to claim 4, characterized in that the diagnostic request is not carried out until the operating state of the internal combustion engine occurs spontaneously without a boost pressure being generated by means of the fresh gas compressor (8).

7. Method according to one of claims 1 to 3, characterized in that the method is applied in an internal combustion engine in which an exhaust gas recirculation line (9) branching off from an exhaust gas line (10) communicates with a fresh gas line (5), via which exhaust gas line (10) exhaust gases of the combustion engine (1) can be discharged, wherein an exhaust gas recirculation valve (13) integrated in the exhaust gas recirculation line (9) is kept at least partially closed during the generation of the negative pressure.

8. The method as claimed in claim 7, characterized in that it is applied in an internal combustion engine in which the exhaust gas recirculation line (9) communicates with a section of the fresh gas line (5) between a control valve (15) and a fresh gas compressor (8).

9. A method according to any one of claims 1 to 3, characterized in that the method is applied in an internal combustion engine in which a throttle valve (21) is integrated in a section of the fresh gas line (5) between a fresh gas compressor (8) and a combustion engine (1), wherein the throttle valve (21) is kept at least partially open during the generation of negative pressure.

10. A method according to any one of claims 1 to 3, characterized by generating a fault record in a fault memory upon identification of a leak.

11. Method according to one of claims 1 to 3, characterized in that the implementation of the measures for limiting the drive rotational speed of the fresh gas compressor (8) is started when a leak is identified.